Electromagnetic radiation such as that generated from radio frequency transmitters and heterodyne receivers or as emitted by electrical circuits utilizing time varying signals as a by-product of their normal operation, can cause unwanted signals manifested as interference or noise to be induced in other devices. This interference is often referred to as Electromagnetic interference or EMI. EMI, which can be a result of spurious emissions and responses, intermodulation products, and the like can interrupt, obstruct, or otherwise degrade or limit the effective performance of the devices with which they interfere. EMI has long been recognized as a source of interference or disruption to various electrical and electronic devices.
EMI can have significant adverse impacts in a variety of environments, including at home, in the workplace, and in other environments where electronic devices are operating. For example, the healthcare environment is one such environment that is particularly plagued by the effects of EMI. Part of the reason for this is that healthcare facilities are typically environments rich with medical and other devices susceptible to adverse effects of EMI. Unfortunately, because devices in healthcare facilities are, in most cases, dedicated to lifesaving and other health-related purposes, interference with these devices can have a devastating impact on the quality of a person's life or even result in the unnecessary loss of life in some circumstances.
Over the years, many incidents of suspected electromagnetic interference (EMI) with medical devices have been documented and there are several reported instances of physical harm or death as a result of EMI. Here are just a few. In one instance a pacemaker patient reportedly lost consciousness when standing for approximately 2 minutes near a security system tower emanating electromagnetic energy. In a similar incident, a pacemaker patient's pulse dropped from 70 down to 31 beats per minute while being interrogated with a metal detector in an airport. In four separate incident reports, patient ICDs (Implantable Cardioverter-Defibrillator that is implanted under the skin of patients that are at risk of sudden death due to ventricular fibrillation) were reprogrammed into the inactive mode after the patient passed through, or was hand-scanned by, a metal detector. In a similar event, an overinfusion of drugs was reported in a patient as a result of electromagnetic interference with the patient's medicament infusion device and dialysis was required to remove the excess drugs. In another incident, a patient with an implanted spinal cord stimulator patient reportedly experienced a strong shock, followed by subsequent sporadic shocks that resulted in loss of consciousness and hospitalization as a result of EMI.
In the healthcare and other environments, the environment has become crowded with potential sources of EMI, from transmitting devices such as cell phones, emergency transponders, and security systems, to the seemingly more mundane such as vacuum cleaners and other electronic devices. Indeed, extensive laboratory testing by the Center for Devices and Radiological Health (CDRH), part of the Food and Drug Administration (FDA), has confirmed that many devices are susceptible to problems caused by EMI.
As our society continues to develop and embrace new technology, there is a proliferation of potentially interfering devices such as, cellular telephones and wireless networks, just to name a few. Similarly, advancements in technology have also found their way into various medical devices, making them more susceptible in some cases to EMI. Microprocessors and sensitive electronic circuits can be found across the vast range of medical devices from monitoring and diagnostic equipment to life support equipment. In fact, modern hospitals and other healthcare facilities are replete with sensitive electronic equipment for supporting just about every aspect of modern day healthcare.
The proliferation of potentially interfering devices coupled with the proliferation of new technology in medical devices has only served to compound the problem. Unfortunately, the EMI is a complex problem and can be difficult to identify and address. Additionally, effective solutions are often cost prohibitive or impractical to implement. As with other electromagnetic fields, the strength of the electromagnetic field responsible for EMI at a given distance from its source is directly proportional to the radiated power of the transmitter and inversely proportional to the distance. Therefore, depending on the source of the interference, the consequences of EMI with medical devices may as minor as a transient “blip” on a monitor, or as serious as causing malfunction of a critical device leading to death or serious injury.
With the increasing use of sensitive electronics in devices, and the proliferation of sources of EM energy, there is heightened concern about EMI in many devices. While the numbers of reports with possible links to EMI have been steady, these numbers are believed by many to not accurately reflect the increasing occurrence of EMI-related incidents. Indeed, in investigating possible EMI-related problems it is often the case that the EM energy responsible for the event has been shut off or removed from the area.
In many reported EMI cases, the effects appear to result in immediate patient symptoms such as a change in heart rate or overstimulation to nerve tissue. However, in some cases a patient might not immediately associate the adverse interaction with the exposure, yet the possibility of suffering serious consequences remains (as in the cases of drug overinfusion or reversion of an ICD to monitor mode mentioned above). Additionally, with EMI, patients may experience some device interaction while they are within the interfering field, but the noticeable effects of the EMI may quickly diminish once the patient has exited the system.
Thus, for these and other reasons, the variable and complex nature of EMI disruptions make them difficult to address in a variety of environments, including healthcare facilities, construction sites, airplanes, FAA control towers, power plants, manufacturing facilities, homes and offices, and others. However, depending on the environment in which EMI is a factor, the impacts could range from unnoticeable or minimal to merely inconvenient, to life-threatening or devastating. An approach to addressing EMI in a plurality of environments is warranted.